[j-nsp] acceptable/good laser receive power in case of different interfaces

[Martin T]

Lane,
while browsing the specifications of the optical modules listed in
this "Optical Interface Support—EX 3200 and EX 4200 Switches.pdf"
file:

http://www.juniper.net/techpubs/en_US/release-independent/junos/topics/reference/specifications/optical-interface-support-ex-series.pdf

..all the modules have minimum and maximum launch power which differ
from each other quite a lot. What does this mean? Shouldn't the launch
power be consistent? In addition, what is a "Maximum Receiver
Sensitivity"?


David, Keegan,
thank you for explanation!


In addition, there isn't some sort of connection between Rx power and
Tx power, is there? I mean for example in case the received signal is
low, the transmit signal of the SFP/XFP is increased automatically? As
far as I know and as Lane confirmed, the Tx signal should be always
consistent..


regards,
martin


2011/8/3 Keegan Holley <keegan.holley at sungard.com>:
> 2011/8/2 Joel Jaeggli <joelja at bogus.com>
>
>>
>> if these are sr multimode optics, the -15 number is low the -7 number is
>> marginal and everything else is decent.
>>
>> either the -15 one is quite long ( for sr) or needs to be
>> replugged/cleaned/reterminated
>>
>>
> Yea I agree.  The -15 is a bit low unless it's is at the end of a really
> long, low-quality fiber run I'd clean it and or replace the XFP.  It's
> blasting out at +1 and receiving much less, there could also be a mismatch
> of some sort.  There are lots of ways to mismatch optics and cabling and
> still get link.
>
>
>
>> On Aug 2, 2011, at 2:53 PM, chip wrote:
>>
>> > Depending on whose optics you're using there should be a data sheet
>> > that shows the acceptable Tx/Rx levels for each type available from
>> > your vendor.  I can't seem to locate a document for Juniper at the
>> > moment.  But I assume they shouldn't be that far off from Cisco stuff.
>> > For example, here's a data sheet for the XENPAK module:
>> >
>> >
>> http://www.cisco.com/en/US/prod/collateral/modules/ps2797/ps5138/product_data_sheet09186a008007cd00_ps5455_Products_Data_Sheet.html
>> >
>> > Check Table-2.
>> >
>> > As far as I know, an optic will output power within a specified range
>> > as according to what type it is, SR, LR, ER, ZR, etc...
>> >
>> > Hope that helps a bit.
>> >
>> >
>> > On Tue, Aug 2, 2011 at 5:26 PM, Martin T <m4rtntns at gmail.com> wrote:
>> >> What is the acceptable Rx power in case of SFP/XFP? For example, here
>> >> are XFP Tx and Rx signals from six FXP's:
>> >>
>> >> 1:
>> >> Laser output power                        :  1.2920 mW / 1.11 dBm
>> >> Laser rx power                            :  0.0285 mW / -15.45 dBm
>> >>
>> >> 2:
>> >> Laser output power                        :  0.6420 mW / -1.92 dBm
>> >> Laser rx power                            :  0.3054 mW / -5.15 dBm
>> >>
>> >> 3:
>> >> Laser output power                        :  0.4230 mW / -3.74 dBm
>> >> Laser rx power                            :  0.5092 mW / -2.93 dBm
>> >>
>> >> 4:
>> >> Laser output power                        :  0.4180 mW / -3.79 dBm
>> >> Laser rx power                            :  0.4208 mW / -3.76 dBm
>> >>
>> >> 5:
>> >> Laser output power                        :  1.0920 mW / 0.38 dBm
>> >> Laser rx power                            :  0.1801 mW / -7.44 dBm
>> >>
>> >> 6:
>> >> Laser output power                        :  0.7680 mW / -1.15 dBm
>> >> Laser rx power                            :  0.3337 mW / -4.77 dBm
>> >>
>> >>
>> >> Is there some sort of pattern? It looks like if the Rx signal is
>> >> lower, the Tx is higher? And what can one consider a decent Rx laser
>> >> power level?
>> >>
>> >>
>> >> regards,
>> >> martin
>> >> _______________________________________________
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>> >>
>> >
>> >
>> >
>> > --
>> > Just my $.02, your mileage may vary,  batteries not included, etc....
>> >
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>>
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